Shelter cartridges...Any thoughts?

I seem to have a passion for the underground, un-reviewed kind of audio most times and these cartridges seem like the real deal. But, rather than blow the dough on something that is not going to deliver the performance, I thought that I would see if some Audiogon folks would chime in. The Lyra Helikon was my other choice...but I don't know anything about the 90x...the 500mk2 and 900 have reviews by one or two guys...HELP!